Limitation factors of optical transmission include attenuation, noise, dispersion, polarization mode dispersion, nonlinear effects, etc. Compensation or elimination technologies of nonlinear effects is always a hot research topic. Relatively practical methods include receiving-end digital reverse transmission method, sending-end perturbation pre-distortion method, etc.
In the digital reverse transmission method, dispersion compensation and nonlinear phase compensation are required to be alternately conducted for many times, the more the number of times, the more the power consumption, so that it is unbearable for chips; moreover, a phase adjustment factor in the nonlinear phase compensation is required to be optimally searched, which is difficult to implement. In the perturbation pre-distortion method, a system is required to configure related information to a transmitter, especially exponential integral functions of real numbers and imaginary numbers involved in a perturbation coefficient computation; moreover, the longer the system transmission distance, the more the involved perturbation terms, and the higher the operation difficulty.
Implementation of the above-mentioned nonlinear compensation method is very complicated, and performance improvement is limited. Generally, improvement of parameter Q corresponding to an error rate before error correction is not greater than 2 dB. Therefore, sectors of optical communication research and industry have been studying to seek better nonlinear compensation or nonlinear elimination technologies.